Low voltage miniature freezing unit



June 20, 1961 J. H. BERGMAN 2,988,903

LOW VOLTAGE MINIATURE FREEZING UNIT Filed Sept. 2, 1958 3 Sheets-Sheet 1 INVENTOR JAMES H. BERGMAN ATTORNEYS June 20, 1961 J. H. BERGMAN 2,988,903

LOW VOLTAGE MINIATURE FREEZING UNIT Filed Sept. 2, 1958 3 Sheets-Sheet 2 INVENTOR (/flMEJ H. BfRGM/I/V June 20, 1961 J. H. BERGMAN 2,938,903

LOW VOLTAGE MINIATURE FREEZING UNIT Filed Sept. 2, 1958 s Sheets-Sheet 3 IN VENTOR JAMES BMG/vmv 1 ECTK/C Mo Tala United States Patent 2,988,903 LOW VOLTAGE MINIATURE FREEZING UNIT James H. Bergman, 1102 Perry St., Defiance, Ohio Filed Sept. 2, 1958, Ser. No. 759,376 10 Claims. (Cl. 62- 512.)

This invention relates to refrigeration systems, and more particularly to a compact refrigeration system which is characterized by extremely low input energy requirements and a high degree of portability, and is a continuation in-part of my similarly entitled application, Serial No. 670,994, filed July 10, 1957 now abandoned.

In modern day refrigeration technology, there is a need for compact cooling systems which may be energized from low voltage sources of electrical energy. For instance, the requirements of conventional 110 volt and 220 volt compressor motors have often rendered the use of such units in portable assemblies entirely impossible. It will be thus appreciated that a small compact refrigeration system capable of operation from a 6 volt or 12 volt system would possess obvious advantages. The present invention contemplates a system wherein such advantages are realized by exploiting the characteristics of screw type compressors or small vane type vacuum pumps.

Accordingly, therefore, a primary object of this invention is to provide an efficient cooling system capable of operating on low values of input voltage.

Another object of this invention is to disclose a miniature cooling system which exploits the low energy level required to drive a screw type or vane type vacuum pump or compressor assembly.

A further object of thepresent invention is to teach a small compact cooling system adapted for application .in an extremely limited space.

, vention will be more fully described hereafter, and will be more particularly pointed out in the claims appended hereto.

FIGURE 1 shows a diagrammatic representation of the components and interconnections used in practicing the invention;

FIGURE 2 shows an end View of the refrigeration unit;

FIGURE 3 comprises a sectional view of one of the tubes of the refrigeration unit, and illustrates the structural details thereof;

FIGURE 4 is an exploded view of FIGURE 3;

FIGURE 5 is a cross section taken through the receiver and needle valve, and

FIGURE 6 is a modified form of system constructed in accordance with the present invention.

Turning to the drawings, and more particularly to FIGURE 1 thereof, the numeral 1 indicates generally a refrigeration system constructed according to the teachings of the present invention. The system shown in FIGURE 1 includes a supply tank 2 which is filled with a supply of volatile non-explosive refrigerant fluid such as methylene chloride, Freon 11 or the like. The lattermentioned two refrigerant fluids are particularly desirable because of their capacity to easily reliquify from the gaseous phase at substantially atmospheric pressure.

The rate at which refrigerant fluid is allowed to escape from the tank 2 is governed by a manually operable regulating valve 3. The regulating valve 3 controls the rate at which refrigerant fluid is allowed to enter a re- Patented June20, 1961 frigerating or evaporator unit indicated generally by the reference numeral 5. More particularly, the downstream side of the valve 3 is directly connected by means of conduit 4 to the input header 5A of the refrigerating unit. The unit 5 will be seen to include a number of spaced tubes 6.

A suction conduit 8 is connected between the output header 5B of the refrigeration unit and the input of a screw type compressor assembly or vane type vacuum pump identified generally in the upper portion of the drawings by the reference numeral 9. The refrigeration unit may be bathed in a flow of air by means of a conventional motor-driven fan. The suction conduit 8 earlier referred to terminates in a hood 9A which is mounted to place the output header of the refrigerating unit in communication with the interior of the compressor assembly 9. The compressor assembly 9 may comprise a commercially available unit such as the Armax unit, which is a screw type unit or any make vane type vacuum pump marketed by the A. K. Fans, Limited, of London, England.

The compressor assembly 9 includes a spiral screw 9B centered for rotation therewithin. The screw 9B may be fabricated of any suitable lightweight material, such as aluminum or magnesium 'metal. The peripheral surfaces of the screw 9B are accurately positioned with respect to the compressor housing 9C in order to provide a maximum clearance of several thousandths of an inch therebetween. The purpose of this restricted clearance, of course, is to inhibit any undesirable leakage or gas escape between the screw and the housing. In practising the invention, a clearance of .002" (two thousandths of an inch) was found to yield excellent results. It will be appreciated that the housing 9C may be composed of a suitable lightweight material such as aluminum, magnesium, or the like.

The screw 9B is characterized by a rather large pitch which may vary in accordance with the required size of the compressor. Thus, in a one-inch diameter screw, the lead, or linear advance of the adjacent spirals for each revolution should approximate one inch. In like manner, a two-inch diameter screw should possess a lead of approximately two inches per revolution. Within the housing 9C the screw is journaled for rotation at one end in a bearing support 9D. The bearing support may include a conventional ball bearing device rotatably disposed with respect to the screw.

At the opposite end, the screw is directly coupled to the shaft of an electric motor 10. The motor 10 is centrally mounted within the housing 9C by means of a plurality of radial support members 10A. The electrical conductors which supply energy to the motor 10 enter the housing 9C through an airtight insulating bushing indicated by the reference numeral 11.

The downstream or high side of the compressor assembly 9 is afiixed to a condenser unit which is generally indicated by the reference numeral 12. The condenser 12 is positioned at a relatively small downward angle from the compressor. It has been discovered that an angle of about 10 is sufiicient in the operation of the device of this invention. The unit 12 is comprised of a number of tubes 13 mounted in good heat exchange relationship with a group of fins 14. A conventional motor driven suction fan 15 is mounted to draw a flow of moving air over the fins 14 in order to enhance the abstraction of heat energy therefrom. Both the tubes 13 and the cooling fins 14 are fabricated of a material such as aluminum, copper, or some suitable alloy which is characterized by excellent thermal conductivity.

The condensed refrigerant or saturated vapor appearing at the output of the condenser unit 12 is discharged into a hood 16. The indicated angularity of the condenser unit with respect to the horizontal is for the purpose of accelerating the delivery of the condensed refrigerant to the drain well 16A. The drain well 16A is the lowest point in the hood 16, and is placed in communication with the supply tank 2 by means of a return conduit 17. Conversely, refrigerant gas emerging from the output of the condenser unit into the hood 16 is placed in communication with the regulating valve 3 by means of a return conduit 18.

Continuing with the detailed description, and turning to the structural details of the refrigerating unit, reference will now be made to FIGURE 2 of the drawings. In this view of the refrigerating unit, the disposition of the input header 5A with respect to the tubes 6 is clearly illustrated. The placement of the fins 7, and the configuration of the output header 5B are believed equally evident.

In the illustration provided in FIGURE 3, a broken section of one of the tubes has been shown in order to illustrate the internal configuration. The assembly is seen to include a centrally disposed inner pipe 6A. The annular space between the pipe 6A and the inner periphery of the tube 6 is loosely filled with a quantity of rolled copper screen 6C. Metallic material comprised of a plurality of metallic strands such as copper wool, copper screen, aluminum wool or the like may be used equally well to surround the inner pipe, and enhance heat conduction therefrom. Other suitable materials are fiberglass and granular asbestos. For purposes of this specification, the material employed to fill the annular space around the inner pipe 6A wil be designated as absorbent material whether metallic or non-metallic.

It will be noted in FIGURE '2 and FIGURE 3 that the output header 5B communicates directly with the annular space in each of the tubes 6. The method of delivering refrigerant from those spaces to the compressor assembly 9, via suction header 8, will be appreciated more clearly as the detailed theory of the invention continues.

Turning now to the method of operation, it will be appreciated that the system is initially charged with liquid refrigerant and is sealed with a small vacuum of about inches existing therein. Prior to energizing the system, it is desirable that a predetermined quantity of refrigerant fluid be present in each of the inner pipes 6A. The compressor assembly may then be energized to provide a high vacuum within the suction conduit 8 and cause freezing conditions on this side of the unit. A pressure is simultaneously generated on the condenser side of the compressor assembly in order to condense the saturated vapors drawn therethrough into liquid form below atmospheric pressure. The high speed of the vane pump or fan blades also condense the vapor to liquid.

Thus, as a result of the delivery of electrical power to motor 10, the rotation of the screw 9B acts to create a vacuum in the hood 9A, the suction conduit 8, and the output header 5B. This vacuum, of course, makes its effect felt within the input header 5A as far back as the regulating valve 3.

Because of the vacuum existing on the downstream side of valve 3, refrigerant liquid is drawn through the valve at a predetermined rate. Additionally, gas from within the return conduit 18 is also drawn through the valve.

Atomized refrigerant drawn into the input header 5A is caused to enter the perforated inner pipe 6A provided within each of the tubes 6. From within these individual inner pipes, the refrigerant saturated gas is drawn through the various linearly spaced orifices 6B by the suction, and distributed throughout the absorbent material 60 provided around the pipes. The moving flow of gas which passes through the orifices 6B into the finely subdivided material 6C is caused to become thoroughly saturated with the refrigerant. This is caused by the refrigerant becoming evaporated and entrained in the quantity of gas. The eficiency and rapidity of this volatilization and saturation process are sufiicient to produce low tempera- 4 tures within the component tubes of the refrigeration unit.

The saturated gas drawn into the output header SE from tubes 6 is conveyed directly to the compressor assembly by suction conduit 8. The screw fan or vane pump 93 compresses the saturated gas and forces it to traverse the various tubes 13 provided in the condenser unit. The flow of cool air drawn through the fins 14 by the fan 15 depresses the temperature of the air and refrigerant passing through the condenser tubes.

The recovered liquid refrigerant emerges from the condenser unit into the drain well 16A provided within the hood 16, and is conveyed back to the supply tank 2 by means of the return conduit 17. In like manner, gas emerging from the condenser into hood 16 is conveyed by return conduit 18 to the regulating valve 3. It will be appreciated that higher values of pressure as well as vacuum may be readily obtained by employing additional screw type compressor assemblies. The placement of an additional compressor assembly in series with the assembly 9 is indicated diagrammatically by the reference numeral 9' in FIGURE 1 of the drawings.

It is pointed out that the novel apparatus of this invention lends itself uniquely to use when low voltage currents are the only currents available. By employing a screw type compressor or vane pump, fairly low vacuum may be obtained even though the motor is operated at low voltages. A piston type compressor would not, under the circumstances present, operate as efiiciently and effectively. The system employs a mixture of gas and liquid refrigerant, since it is not desirable under the conditions to permit a vacuum when the refrigerant is condensed. In the system of this invention the gas operates to fill the void, leaving only a partial vacuum. The use of a condenser for the liquified refrigerant and which is at a slight angle for delivery of the refrigerant to a well insures that the liquid is separated from the partial vacuum conditions that exist after the condenser stage. It should be appreciated that it would not be desirable to permit the refrigerant to vaporize again at a point before the refrigerating unit 5. Additionally, the provision of a unique evaporative system such as shown by refrigerating unit 5 allows the suction created by the vacuum pump to be effective all the way back to the valve 3. The total result of the ingenious system is to make it possible to effect a refrigeration cycle employing low voltage current as the power source.

Modified form of invention In a standard refrigerating system, the unit consists of a compressor, condenser, evaporator and expansion valve. The compressor is run on current from volts on up depending on the size of the unit. The compressor compresses the saturated vapor into the condenser. The heat is taken out and the gas is liquified. The liquid goes into a receiver connected to an expansion valve. This is called the high side of the line.

The liquid comes out of the expansion valve into the low side of the line, where it expands and cools in the evaporator. This system uses what is called a normal pressure, which goes over one hundred pounds. There are many models, name brands and many designs of re frigerating systems but they use 110 or more volts of power, and high pressure on the high side and a lower pressure on the low side.

In the miniature low voltage freezing unit, shown in FIGURE 6, no high pressure is used, and it is operated on a low voltage of 2, 6 or 12 volts depending on the small size designed. This system can use storage batteries or small batteries combined with the unit which makes it a portable unit and can be carried anywhere without stringing wires to the source of power.

The system employs in FIGURE 6 a vane pump 9 or any other means for circulating the gases. There is not much load carried by the pumps, as there is no pressure on the high side. There is a small amount of friction in the floating seal in the use of the pumps but not much friction when using a screw type compressor. The only work the vacuum pump 9 has is in the vacuum side when drawing the gas through the needle valve, FIGURE 5. This gas is moved from the needle valve 3 through the evaporator 6, through the pump 9, through the condensers 12-19, then back to the needle valve 3.

In the standard refrigerating system, the liquid is forced through the expansion valve by pressure on the high side, and low pressure on the low side. On the miniature low voltage unit the liquid is trapped or flows into a receiver 2. In this receiver 2 there is a tube extending to the bottom of the receiver. It extends out of the top and into the horizontal pipe 18 leading from the condenser. The pipe coming from the bottom well of the condensers 1219 are the liquid pipes, and it goes into the bottom of the receiver, or near the top, just so the liquid from the condensers 1219 can get into the receiver 2. The needle valve 3 extends through from the top of the horizontal pipe 18 vertically and is adjustable so that the needle will close the vertical pipe coming from the receiver or open the pipe end. This is the needle valve 3. As the pump 9 is started, this causes a suction in the horizontal pipe containing the needle valve. This suction causes the liquid to emerge from the vertical tube and atomizes the liquid. The amount of liquid emerging can be preset or varied with the needle valve 3. As the liquid vaporizes, beginning at the valve, its temperature drops or cools considerably. The gas that goes through the needle valve 3 comes from the condenser. There are two pipes or lines coming from the condenser 12. One contains the gas and the other contains the liquid. The liquid that is atomized out of the needle valve is sucked or drawn out, by suction and not by pressure. The very high vacuum at the needle valve 3 causes the quick drop in temperature.

The drawing of this liquid out of the tube by suction is the same as gasoline is drawn through a carburator by'air in a gasoline engine.

The unit is pumped free of air, or partially, to a vacuum of from 5 inches to 20 inches vacuum. The amount of vacuum in the unit depends on the kind of refrigerant used. When the pump 9 is started, a higher vacuum results at the low side of the needle valve 3. The more liquid that is allowed to escape from the needle valve, and the amount of gas drawn through the tube connecting the valve with the condenser, or volume of gas, depends on the size of the unit, size of the pump 9 and capacity of the evaporator 6.

A refrigerant with a too low boiling point, such as Freon 12, which is -22 at atmospheric pressure, will cause a high pressure in the system and will not work. Methylene chloride with a boiling point of 104 F. will work. Freon 11 with 74 F. will work. Freon 114 with 38 F. boiling point will work. As the boiling point goes down, the pressure goes up. As the boiling point of a liquid goes up, the pressure goes down in this system.

Methylene chloride is charted at 32' degrees, at a vacuum of about 27 inches. With this unit the gauge on the vacuum pump shows 15 inches vacuum and the thermometer shows freezing and the evaporator freezes. Freon 11 was used and the chart shows zero temperature at 25 inches vacuum. This unit showed zero at 20 inches.

In one experiment a very small vacuum pump 9 was used that had a limited top vacuum of inches. A vacuum was created in the unit of 10 inches then sealed. With the pump running, the total vacuum could not be over 20 inches, but it showed from freezing to 20 below Zero according to the d'iiferent chemicals or refrigerants used. One hundred twenty square inches of copper tubing was frozen on the outside.

There is a very decided drop in vacuum immediately after passing the needle valve.

The needle valve is made like a Venturi tube. As the gas enters the tube it is compressed somewhat in the throat of the Venturi tube. As it leaves the tube, it expands.

This system is somewhat like the centrifugal system and uses the vane or screw pump for compressing the saturated gas back into a liquid with the help of the cooling fan blowing through the condenser.

Although I have disclosed herein the best forms of the. invention known to me at this time, I reserve the right to all such modifications and changes as may come within the scope of the following claims.

What is claimed is:

1. A low voltage miniature freezing unit comprising a supply tank :for housing liquid refrigerant, an evaporator unit mounted to communicate with said supply tank, means including a vane type pump compressor assembly mounted to induce a flow of saturated gas into and through said unit, condenser unit means connected to said last-mentioned means for partially condensing gaseous refrigerant and separating liquid and gaseous refrigerant, and return conduit means for conveying said liquid refrigerant to said supply tank.

2. A low voltage miniature freezing unit with predetermined quantities of liquid refrigerant and gas contained therein comprising a closed loop refrigeration system having an evaporator unit having a plurality of tubes provided with absorbent material therein, means including a vacuum pulling compressor assembly for drawing a mass of gas as well as a quantity of liquid refrigerant into said unit and distributing said refrigerant throughout said absorbent material, condenser means mounted to receive a flow of saturated gas as it emerges from said compressor assembly and to partially condense said gas, means including conduit means connected to separately receive quantities of liquid refrigerant and gas separated within said condenser means and redistribute same individually into said unit.

3. The low voltage miniature freezing unit of claim 2 wherein said absorbent material comprises rolled metallic mesh.

4. The low voltage miniature freezing unit of claim 2 wherein said compressor has an impeller comprising a helical vane.

5. A low voltage miniature freezing unit comprising a compressor, an evaporator connected to supply refrigerant to said compressor, condenser and separator means connected to receive refrigerant from said compressor and condense and separate liquid and vapor stages of said refrigerant, said evaporator receiving refrigerant from said condenser and separator means and comprising an input header for receiving refrigerating gas and refrigerating liquid, subdivided absorbent material in said evaporator, means connected to said input header for introducing refrigerant fluid into said absorbent material at spaced points tothereby distribute said refrigerant throughout said absorbent material, and means including an output header connected to communicate with said absorbent material and provide egrees to the mixture of gas and volatized refrigerant generated therein.

6. A device as claimed in claim 5 in which said absorbent material is fiberglass.

7. A device as claimed in claim 5 in which said absorbent material is granular asbestos.

8. A device as claimed in claim 5 in which said absorbent material comprises a plurality of strands of metallic material characterized by high thermal conductivity.

9. A low voltage miniature freezing unit comprising a compressor, an evaporator connected to supply refrigerant to said compressor, condenser and separator means connected to receive refrigerant from said compressor and condense and separate liquid and vapor stages of said refrigerant, said evaporator receiving refrigerant from said condenser and separator means and comprising an input header for receiving refrigerating gas and refrigerating fluid, at least one inner pipe connected to communicate with said input header, said inner pipehaving a plurality of orifices therealong, at least one tube provided with a plurality of cooling fins and concentrically mounted with respect to said inner pipe, a quantity of heat transferent material disposed Within the annular internal volume defined by said inner pipe and the interior surface of said tube, and an output header connected to communicate with said heat transferent material disposed within said annular volume.

10. A low voltage miniature freezing unit comprising a closed loop refrigeration system having an evaporator, a compressor and a condenser, said condenser delivering liquid and gaseous refrigerant therefrom, means for separating the liquid refrigerant from the gaseous refrigerant delivered by said condenser, a refrigerant tank, means connected to said separating means and said tank for conducting liquid from said means to said tank, a conduit connected to said separating means to receive gaseous refrigerant therefrom, aspirating means connected to said conduit and to said tank for aspirating liquid refrigerant from said tank by gaseous refrigerant flowing from said separating means. conduit means connected to said aspirating means and said evaporator for conducting refrigerant from said aspirating means to said evaporator, and conduit means connected to said evaporator and compressor for conducting refrigerant from the evaporator to the compressor.

References Cited in the file of this patent UNITED STATES PATENTS 1,809,833 Davenport June 16, 1931 2,131,453 Patteson Sept. 27, 1938 2,159,251 Brizzolani May 23, 1939 2,277,647 Jones Mar. 24, 1942 2,548,441 Morrison Apr. 10, 1951 2,785,542 Thomas Mar. 19, 1957 

